Directed gas injection apparatus for semiconductor processing

ABSTRACT

A method and system for utilizing a gas injection plate comprising a number of shaped orifices (e.g., sonic and simple orifices, and divergent nozzles) in the gas inject system as part of a plasma processing system. By utilizing the shaped orifices, directionality of gas flow can be improved. This improvement is especially beneficial in high aspect ratio processing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending application Ser. No.60/272,452, filed Mar. 2, 2001 entitled “SHOWER-HEAD GAS INJECTIONAPPARATUS WITH SECONDARY HIGH PRESSURE PULSED GAS INJECTION” andco-pending application Ser. No. 60/301,413, filed on Jun. 29, 2001entitled “DIRECTED GAS INJECTION APPARATUS FOR SEMICONDUCTORPROCESSING”. This application is also related to and claims priority toco-pending application Ser. No. 60/301,436, filed on Jun. 29, 2001. Thecontents of those applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a method and system for utilizing ashaped orifice or nozzle in a plasma processing system.

2. Discussion of the Background

During the fabrication of integrated circuits (IC), a conventionalapproach to oxide etch employs a capacitively coupled plasma (CCP)source, wherein a process gas comprising argon, C_(x)F_(y) (e.g. C₄F₈),and O₂ is introduced to a low pressure environment to form plasma.Therefrom, the plasma dissociation chemistry is tuned for optimalproduction of the chemical reactant suitable for chemically reactingwith the substrate surface material to be etched (i.e., CF₂ forselective oxide etch). Moreover, the plasma further produces apopulation of positively charged ions (e.g. singly charged argon Ar⁺)suitable for providing energy to the substrate surface to activate theetch chemistry. In general, a substrate RF bias is employed to attractions to the substrate surface in a controllable, directional manner toaffect the ion energy at the substrate surface and to provide ananisotropic etch for desired feature side-wall profiles.

Due to the differing roles of the atomic, molecular and ionic speciespresent in the plasma, it is believed that oxide etch comprises twofundamentally unique processes. Firstly, electrons are heated in theplasma whereby collisions with fluorocarbon species leads todissociation and formation of radical species, e.g. CF₃, CF₂, CF, F,etc. And secondly, electrons are heated to energies sufficient to ionizeargon atoms, whereby the resultant ions are utilized to energizesubstrate surface CF_(x)/SiO₂ chemical reactions.

For instance, referring to FIG. 1, an exploded view of an etch featurein an oxide layer is shown. In the plasma, fluorocarbon radicals areformed. Thereafter, they diffuse to the substrate and deposit onto theetch feature surfaces. Preferably, an increased concentration of CF₂radical local to the wafer surface can lead to several advantages(Nakagawa et al. 1998, Booth 1998, Kiss et al. 1992, Butterbaugh et al.1991, Tatsumi et al. 1998), in particular: (1) the formation of a CF_(x)polymer layer atop the patterned photoresist tends to protect the resistduring the etch process for improved selectivity of SiO₂-to-resist etch,(2) the formation of CF_(x) polymer layer along sidewalls providesprotection for improved etch anisotropy, and (3) the formation of CF₂ atthe bottom of a feature provides a suitable etch reactant for selectiveetch of oxide relative to silicon that produces volatile products, i.e.one of many chemical reactions can be 2CF₂+SiO₂→SiF₄+2CO. Thereafter,the directional nature of the ion bombardment of the substrate surface,as shown in FIG. 2, leads to an anisotropic etch, wherein the argon ionenergy is sufficient to activate the etch chemistry in the etchfeatures.

One technique proposed in the archival literature as described above toimprove high aspect ratio contact etch in oxide (e.g., etch rate,side-wall profile, selectivity, etc.) suggests optimization of theplasma chemistry to form CF₂ radical. In doing so, studies have shownthat the concentration of fluorocarbon radicals, particularly CF₂,correlate well with τn_(e)

σν

, where τ is the gas residence time, n_(e) is the electron density, σ isthe dissociation collision cross-section, v is the electron velocity and

σν

is the integration of the product σν with the normalized electron energydistribution function (Tatsumi et al. 1998). Hence, conventionalpractice entails adjusting the plasma density to optimize theconcentration of the preferred etch radical to achieve the enumeratedconditions above and, in general, for oxide etch it can lead tolimitations on the maximum etch rate. This shortcoming is often governedby the demand for meeting an etch selectivity specification or aside-wall profile specification. For instance, the etch rate istypically proportional to the plasma density (ion density equals theelectron density for a quasi-neutral plasma, and either can be referredgenerally as the plasma density), whereas the etch selectivity can beinversely proportional to the plasma density once the plasma density issufficiently large to produce a highly dissociated radical concentration(i.e., high fluorine radical concentration for etching oxide withC_(x)F_(y) process chemistry). Moreover, inappropriate chemistry due toexcessively high dissociation rates can lead to inadequate protection offeature side-walls and therefore jeopardize side-wall profiles leadingto an isotropic etch. Lastly, insufficient plasma density and lowdissociation (i.e., high concentrations of CF₃, CF₂, etc.) can lead toetch stop due to material (i.e., C) build-up at the bottom of etchfeatures. Therefore, due to the close relationship between the plasmadensity and the preferred radical concentration, this results in a verynarrow parameter space wherein one must work to achieve marginallyacceptable performance specifications for etch rate, etch selectivityand side-wall profile (or anisotropy). This is a major shortcoming forconventional hardware and process practice particularly since the etchrequirements vary during the period one etches a deep, high aspect ratiocontact.

For a typical shower-head gas injection system utilized in aconventional semiconductor processing device, the inject plate generallycomprises an array of several hundred (several hundred to severalthousand) inject orifices through which gas is introduced to theprocessing region at a flow rate equivalent to 100–1000 sccm argon.Furthermore, the injection orifice is typically a cylindrical orifice asshown in FIG. 3 characterized by a length L and diameter d, wherein theratio of the orifice length to the orifice diameter L/d is greater than10 (i.e., L/d>>1). For instance, a typical orifice diameter is 0.5 mmand a typical orifice length is 1 cm, and therefore the aspect ratioL/d=20.

As a consequence of this design, the gas effuses from the orifice exitwith a very broad angular distribution characteristic of a low dischargecoefficient orifice. The discharge coefficient of an orifice C_(D) isgiven by the ratio of the real mass flow rate to the isentropic massflow rate. The isentropic mass flow rate can be derived from the Eulerequations (or inviscid Navier-Stoke's equations) for a quasi-onedimensional frictionless and adiabatic flow, viz.

$\begin{matrix}{{m_{isentropic} = {{P_{t}( \frac{\gamma + 1}{2} )}^{{- 1}/{({\gamma + 1})}}\sqrt{\frac{2\gamma}{\gamma\mspace{11mu} R\;{T_{t}( {\gamma + 1} )}}}A}},} & (1)\end{matrix}$where γ is the ratio of specific heats for the gas, R is the gasconstant, P_(t) is the total pressure, T_(t) is the total temperatureand A is the minimum cross-sectional (throat) area (i.e., A=πd²/4). WhenC_(D)<<1, the total pressure recovery through the orifice is severelyreduced and hence the angular distribution of the orifice flux becomesvery broad. Therefore, a shortcoming of conventional gas injectionsystem designs is a relatively low gas injection orifice dischargecoefficient.

Furthermore, conventional systems suffer from a lack of control of thegas injection orifice discharge coefficient. In many cases, the gasinjection orifice is subjected to erosion and, hence, the gas injectionproperties vary in time during a process, from substrate-to-substrateand batch-to-batch. Conventional systems do not monitor the state of a“consumable” gas injection system nor do they attempt to control the gasinjection properties to prolong the life of a “consumable” gas injectionsystem.

In addition to gas injection orifices with an uncontrollable dischargecoefficient, conventional designs suffer from an additional shortcoming.That is the gas injection orifices are not oriented relative to oneanother to provide a uniform, directional flow local to the substratesurface.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a gas injectionsystem design comprising one or more gas injection orifices tailored toimprove one or more of: (1) the orifice discharge coefficient, (2) thegas flow directivity at the orifice exit, and (3) the flux of chemicalspecies normal to the substrate surface.

It is a further object of the present invention to provide a gasinjection system design comprising a plurality of gas injectionorifices, each of which is arranged relative to one another to improvethe spatial uniformity of the flux of chemical species normal to thesubstrate surface.

It is another object of the present invention to provide a gas injectionsystem design comprising one or more gas injection orifices, a sensor tomonitor an intrinsic gas injection parameter and a controller, the useof which enables monitoring the state of the one or more gas injectionorifices. The state of the gas injection orifices can be used todetermine consumable replacement and the current state of the gasinjection orifices can be used to return the current state to the designstate, hence controlling the gas injection orifices and prolongingconsumable lifetime.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a high-aspect ratio feature being etched bya fluorocarbon plasma;

FIG. 2 is a cross-section of a high-aspect ratio feature being etched inthe presence of an Argon plasma;

FIG. 3 is an enlarged cross-section of a shower-head injection orifice;

FIG. 4 is a schematic cross-section of a material processing systemaccording to an embodiment of the present invention;

FIG. 5A is a sonic orifice according to the first aspect of the presentinvention;

FIG. 5B is a divergent nozzle according to a second aspect of thepresent invention;

FIG. 5C is a simple orifice according to a third aspect of the presentinvention;

FIG. 6 is a graph showing a relation between orifice Knudsen number Knand orifice aspect ratio L/d, and discharge coefficient;

FIG. 7 is a schematic illustration of a probability distributionfunction of gas velocity angle local to the substrate surface;

FIG. 8 is a schematic cross-section of an embodiment for a gas injectionorifice spacing;

FIG. 9 is a schematic plan-view of an embodiment for a gas injectionorifice spacing;

FIG. 10 is a schematic illustration of a method to fabricate gasinjection orifices;

FIG. 11 is a procedure to fabricate gas injection orifices;

FIG. 12 is a schematic representation of the inject total pressureduring gas injection orifice erosion;

FIG. 13 is a photograph of a gas injection orifice subjected to plasmaerosion;

FIG. 14 is an exemplary representation of a control path for adjustingthe discharge coefficient; and

FIG. 15 illustrates a simplified block diagram of a manufacturing systemin accordance with a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to improve etch rate, etch selectivity and etch featureside-wall profile, the present invention improves a gas injection designutilized in a material processing device to affect improvements inchemical transport local to an exposed substrate surface. (As usedherein, “substrate” means any workpiece processed in a plasmaenvironment, including, but not limited to semiconductor wafers andliquid crystal display panels.) The exposed substrate surface is exposedto either material etch or deposition steps, the combination of whichserve to alter the material composition and/or topography of the exposedsubstrate surface. When the material processing device utilizes aprocessing plasma, the improvements to the chemical transport can affectthe dissociation chemistry and hence radical concentrations, as well asaffect radical transport near the substrate surface high aspect ratiofeatures. The present invention utilizes an improved gas injectionorifice design to maximize the orifice discharge coefficient and aspacing of gas injection orifices to provide a uniform, directional gasflow normal to the substrate surface.

FIG. 4 illustrates a schematic representation of a material processingsystem 1 comprising processing chamber 10 wherein processing region 12is provided. The processing region 12 preferably contains a gas atreduced pressure and plasma. The material processing chamber 10 furthercomprises upper gas injection plate 20 through which processing gas 25enters processing chamber 10. Additionally, chamber 10 providessubstrate holder 30 upon which substrate 35 rests, wherein an uppersurface of substrate 35 is exposed to processing region 12. Furthermore,the substrate holder 30 can be vertically translated by a substrateholder translation device 36 such that the spacing, h, between theexposed surface of substrate 35 and gas injection plate 20 can bevaried. Effluent gas from processing region 12 is exhausted throughchamber port 38 to vacuum pump 40. The materials processing system 1further includes controller 42 coupled to mass flow controller 44,pressure sensor 46, gas supply 48, vacuum pump 40 (gate valve, etc.),chamber pressure sensor 49. Improvements to the design of the gasinjection plate 20 can facilitate improvements in material processing ofthe substrate 35, and these features are described below.

FIGS. 5A, 5B, and 5C present three exemplary embodiments of a gasinjection orifice according to the present invention. The firstcross-section (FIG. 5A) is referred to as a sonic orifice having throat45 with throat diameter d (e.g., d is on the order of 0.025 to 0.5 mm)and first sidewall 50 with length L. Preferably, the aspect ratio L/d ismuch less than unity (i.e. L/d<<1). The discharge coefficient (asdefined above) is very sensitive to the ratio of the length L of theminimum area cross-section (e.g., first sidewall 50) to the diameter dof the minimum area cross-section (e.g., throat 45). Generally, firstsidewall 50 of throat 45 is parallel to orifice centerline 55. The gasinjection orifice further includes an inlet 65 to permit gas to enterorifice throat 45. Depending upon the thickness of the material withinwhich the gas injection orifice is fabricated, the orifice inlet 65 cancomprise a passage with second sidewall 70 of a finite entry length anda cross-sectional area substantially greater than the cross-sectionalarea of the throat 45. For example, the cross-sectional area of inlet 65is preferably a factor of ten (10) greater than the cross-sectional areaof throat 45. The design of inlet 65 is such that gas passes betweensecond sidewall 70 until the gas arrives at throat entry wall 75 priorto throat 45. In one embodiment (not shown), the throat entry wall 75remains flat until the first sidewall 50 (where the opening for thethroat 45 begins).

In the illustrated embodiment, shown in FIG. 5A, the throat entry wall75 comprises a slope (having an angle α indicated as 80 in FIG. 5A)between the throat entry wall 75 and the orifice centerline 55 (therebyforming a conical section at the entrance to throat 45). The entranceangle 80 is preferably 45 degrees; however, entrance angle 80 of throatentry wall 75 can vary from 30 to 90 degrees as described above (anentrance angle 80 of 90 degrees is equivalent to a “flat” throat entrywall 75 as described above).

FIG. 5B illustrates a cross-section of a second embodiment of an injectorifice, namely a divergent nozzle. The divergent nozzle includes athroat 45 of diameter d (e.g., d is on the order of 0.025 to 0.5 mm) anda corresponding aspect ratio L/d<<1 (e.g., L/d<0.5). Beyond the nozzlethroat, there exists a conically divergent section that undergoes adiameter increase from the throat 45 of diameter d to the exit 85 ofdiameter d_(e) with an exit diameter ratio d_(e)/d on the order of 4.The purpose of the conical section is to restrain the rate at which thegas expands into the low pressure environment. In general, the angle βindicated as 90 in FIG. 5B should not exceed approximately 18 degrees inorder to minimize radial flow losses and possibly deter flow separationfrom the nozzle walls. In addition, a small angle can lead to excessivenozzle lengths for a given area ratio as well as increased frictionlosses. The angle 90 is preferably 5<β<20 degrees, and more preferably15<β<20 degrees. The conical section can be replaced with a concavesection, particularly a smooth wall contour designed using the Method ofCharacteristics (i.e., a “perfect” nozzle or “minimum-length” nozzle).If one wishes to maximize the mean (spatial) pressure sensed at thesubstrate surface, one would choose the sonic orifice when Kn>0.005 andone would choose the divergent nozzle when Kn<0.005, assuming a Knudsennumber Kn derived from an estimation of the mean free path estimatedusing the variable hard sphere (VHS) model; Bird, G. A., Molecular gasdynamics and the direct simulation of gas flows, Clarendon Press, Oxford(1994).

In a third embodiment, shown in FIG. 5C, the inlet 65, entry region withwalls 70 and throat entry wall 75 are removed, and the gas injectionorifice is fabricated within a piece of material of thickness equivalentto the length L of wall 50 (or throat 45). The embodiment described inFIG. 5C is hereinafter referred to as a simple orifice.

In summary, the difference in gas orifice geometry between (1) ashowerhead orifice and (2) a shaped orifice or nozzle (e.g., a sonicorifice or a divergent nozzle) leads to significantly different flowconditions.

FIG. 6 presents the measured discharge coefficient versus the orificeKnudsen number Kn. The orifice Knudsen number represents the ratio ofthe mean free path at total (or stagnation) conditions to the throatdiameter d. Note that Kn<0.01 signifies the continuum regime, 0.01<Kn<1signifies the transition regime, and Kn>1 signifies the free molecularflow regime. Clearly, the discharge coefficient is significantly largerfor an aspect ratio of L/d=0.5 versus and aspect ratio L/d=20 (by afactor of 4 to 5), for a wide range of Kn.

The discharge coefficient for the sonic orifice can lead to a narrowangular distribution of the orifice flux. In other words, an increase inthe inject total pressure (or decrease in the Knudsen number) and/or ahigh discharge coefficient can produce a highly directed gas jet.

With continuing reference to FIGS. 5A–C, a gas injection orifice designwas described to increase or maximize the discharge coefficient C_(D)(shown in FIG. 6). However, more generally, a relationship between thegas injection performance local to the orifice and two locally definedparameters, namely the orifice aspect ratio L/d and the orifice Knudsennumber Kn, was established. Therefore, a parameter Π₁, e.g. a measurablesuch as the discharge coefficient C_(D), can be described by these twoparameters, i.e. C_(D)=C_(D)(L/d, Kn). For example, by using the rulesof non-dimensional analysis, the above parameters are madeinterchangeable, and one can re-write the above expression asΠ₁=Π₁(C_(D), L/d). From experiment, the gas injection orifice design,described by the above expression, strongly affects the number densityproximate the exposed surface of substrate 35 and to second order itaffects the probability distribution function of the incidence angle (atthe surface of the substrate) to be described below.

Referring now to FIG. 4, process gas 25 enters processing region 12through a gas injection plate 20, wherein surface 22 of gas injectionplate 20 is substantially parallel to the exposed surface of substrate35. For example, process gas 25 is injected in a direction substantiallynormal to the surface of substrate 35. An exemplary probabilitydistribution function (PDF) of the gas velocity angle χ relative to thesurface normal vector at the surface of substrate 35 is shown in FIG. 7for a location directly below a gas injection orifice in gas injectionplate 20. Therefore, it is most probable at this location thatatoms/molecules are moving normal (striking at an angle indicated inFIG. 7 as 300) to the surface of substrate 35 (however, this observationis not true when one moves laterally away from a location directly“in-line” with a gas injection orifice). The “narrowness” or “broadness”of the PDF is strongly dependent on the background pressure and thespacing h between the surface 22 of gas injection plate 20 and theexposed surface of substrate 35. Furthermore, the probabilitydistribution function of the incidence angle PDF(χ) is strongly affectedby the relative spacing of the gas injection orifices Δs in gasinjection plate 20 to the spacing h between the exposed surface ofsubstrate 35 and gas injection plate 20.

In order to affect change in the mass transport proximate the exposedsurface of substrate 35 (or the entrance regions to etch or depositionfeatures), two dependent parameters, described above, are available. Theflux of mass into an etch or deposition feature is dependent on: (1) thegas number density proximate the exposed surface of substrate 35, and(2) the probability of an atom/molecule striking the surface at an anglesubstantially near normal incidence. Considering the above discussion, asecond property Π₂ is expressed as a function of the dischargecoefficient C_(D), the orifice aspect ratio L/d, the relative gasinjection orifice spacing Δs/h (where Δs is the gas injection orificespacing on gas injection plate 20 and h is the spacing (or distance)between the gas injection plate 20 and the exposed surface of substrate35) on gas injection plate 20 and a chamber Knudsen number Kn_(c), i.e.Π₂=Π₂ (C_(D), L/d, Δs/h, Kn_(c)). The first two dependent variables(C_(D) and L/d) are related to the design of the gas injection orificeas discussed with reference to FIGS. 5A–C. The design of the gasinjection orifice can strongly affect the gas number density proximatethe exposed surface of substrate 35 and to a lesser degree the incidenceangle probability distribution function. The third variable relates tothe relative spacing of gas injection orifices on gas injection plate 20and strongly affects incidence angle probability across the exposedsurface of substrate 35. The preferred selection of Δs/h is discussedbelow. Lastly, the fourth variable is a Knudsen number based uponchamber conditions or the background pressure; i.e. Kn_(c)=λ_(c)/h,where λ_(c) is the mean free path defined using the (background) chamberpressure. For example, when Kn_(c) is large, PDF(χ) is narrow and, whenKn_(c) is small, PDF(χ) is broad.

To affect changes in the transport properties proximate substrate 35,the first dependent variable described above (related to gas injectionorifice design), the discharge coefficient C_(D), can be adjusted duringsubstrate processing and from wafer-to-wafer, and the second dependentvariable, the orifice aspect ratio L/d, can be designed a priori. Inother words, the aspect ratio (although varying during processing due toplasma erosion of the orifice) is generally not controllable. Changes toC_(D) can be achieved via changes to the injection total pressure (ormass flow rate). For example, an increase in the injection totalpressure (or an increase in the mass flow rate) can cause an increase inthe discharge coefficient. The adjustment of C_(D) is described ingreater detail below.

To affect changes in the transport properties proximate substrate 35,the third variable, the relative spacing Δs/h, can be adjusted duringsubstrate processing and from substrate-to-substrate through changes toh via vertical translation of substrate holder 30 using translationdevice 36.

To affect changes in the transport properties proximate substrate 35,the fourth variable, the (background) chamber Knudsen number Kn_(c), canbe adjusted during substrate processing and from substrate-to-substrate.Changes to Kn_(c) can be affected through changes either to the spacingh, and/or the (background) chamber pressure via translation device 36and mass flow rate and/or vacuum pump throttle valve setting coupledwith chamber pressure sensor 49, respectively.

Still referring to FIG. 7, in order to maximize the probability offinding an atom/molecule moving in a direction substantially normal tothe surface of substrate 35, or within a specified angular range 310,the spacing of gas injection orifices is determined according to thefollowing relationΔs=2h tan(φ),  (2)where Δs is the gas injection orifice spacing as indicated by 400 inFIG. 8, φ is an acceptable angular deviation (half-angle) from normalincidence as indicated by 410 in FIG. 8, and h is the spacing (ordistance) between the gas injection plate 20 and the exposed surface ofsubstrate 35 as indicated by 420 in FIG. 8. In order to optimize thetransport of mass into an etch or deposition feature, the half-angle φshould coincide with the feature acceptance half-angleφ_(f)=tan⁻¹(d_(f)/21_(f)), where d_(f) is the feature diameter (orlateral length scale) and l_(f) is the feature length (or longitudinallength scale); see FIG. 2. In other words, φ≦φ_(f), or the inverse ofthe relative gas injection orifice spacing h/Δs should coincide with thefeature aspect ratio AR=l_(f)/d_(f), i.e. h/Δs≧AR.

FIG. 9 presents a plan view of a gas injection plate 20 comprising aplurality of gas injection orifices through which process gas 25 flows,wherein the orifices are aligned preferably in a hexagonal pattern suchthat the spacing (Δs) 400 between any given orifice and an adjacent(surrounding) orifice is the same. Lastly, the (background) chamberKnudsen number Kn_(c) is preferably selected such that the full-widthhalf maximum δ_(FWHM) of PDF(χ) is approximately equivalent to twice thefeature acceptance half-angle 2φ_(f) in order to optimize the efficiencyof mass transport into etch or deposition features. For example, whenh=25 mm and AR=10(:1), the (background) chamber pressure isapproximately 2 to 5 mTorr to satisfy this condition.

When coupling together the design criteria for gas injection orificespacing, pattern, chamber conditions and orifice cross-section (i.e.FIGS. 5A, 5B, and 5C), the design of the gas injection plate 20 canuniformly maximize the number of atoms/molecules moving substantiallynormal to the surface of substrate 35 within plus or minus an angularrange 310. For example, by maximizing both the number of atoms/moleculeslocal to the surface of substrate 35 and the probability of finding anatom/molecule moving in a direction substantially normal to the surfaceof substrate 35 the plasma process can be optimized.

For example, in oxide etch, the array of gas injection orificescontinuously injects a process gas (i.e. C₄F₈) diluted with an inert gas(e.g., argon) into the processing region 12. One example of a gas specieprocess recipe can include 300 sccm argon, 5 sccm C₄F₈ and 10 sccmoxygen. For such a flow rate, the inject total pressure is approximately5 Torr for an array of 36000 inject orifices (d=0.05 mm, L=0.025 mm) anda mass flow rate of 400 sccm argon. In such a design, the gas injectionorifices can be spaced every one (1) millimeter in a hexagonal pattern,hence, leading to a uniform, directional flow near the surface of thesubstrate 35 optimized for normal incidence plus or minus one (1) degree(e.g. one (1) degree is less than the requirement suitable for 12:1aspect ratio feature etch or deposition). The gas injection orificespacing (Δs) 400 is determined to be one (1) mm for a distance h betweenthe gas injection plate 20 and the exposed surface of substrate 35 of 25mm (or one inch).

The sonic orifice, divergent nozzle, or simple orifice, as described inFIGS. 5A, 5B, and 5C, can be fabricated using a wide range of materialssuch as stainless steel, aluminum, alumina, silicon, quartz, siliconcarbide, carbon, etc. When fabricated from aluminum, theorifices/nozzles can be anodized to provide erosion protection from theplasma. Furthermore, the gas injection orifices can be spray coated withY₂O₃ to provide a protective barrier. The sonic orifice or divergentnozzle can be manufactured using a broad variety of machining techniquessuch as diamond bit machining, sonic milling, laser cutting, etc., and,in some applications, orifice fabrication can be amenable to etching. Infact, if the total thickness of the material through which anorifice/nozzle is fabricated is of order a millimeter, orifice etchingis within current practical etch rates and reasonable processing times.

For example, FIGS. 10 and 11 describe a method for fabricating one ormore gas injection orifices in a substrate (i.e. 750 micron thickpoly-Si wafer). In FIG. 10, the fabrication steps are illustrated andthe procedure is mirrored in the list of steps provided in FIG. 11. Thefabrication process is started in step 500. Step 510 proceeds with theapplication of a photo-resist film 514 to a first surface of thesubstrate 512 and a pattern 516 is transferred to the photo-resist filmvia photolithography. The patterned feature width can be approximately1400 microns.

In step 520, a feature 522 is wet etched within substrate 512 byimmersing the substrate 512 in a KOH/alcohol solution for a period oftime dictated by the time required to etch the (isotropic) feature 522to a depth of approximately 700 micron or greater. Once the wet etch iscomplete, the photo-resist mask 514 is removed.

In step 530, the substrate 512 is flipped and a second photo-resist film532 is applied to a second (opposite) surface of substrate 512 and apattern 534 is transferred to the photo-resist film 532 viaphotolithography. The patterned feature width can be approximately 50microns.

In step 540, the substrate 512 is dry etched utilizing a SF₆/O₂(/C₄F₈)or Cl₂ chemistry in a plasma processing device well-known to those ofskill in the art and gas injection orifices (d=0.050 mm, L≦0.050 mm) canbe formed. Typical etch rates are 50 micron per minute and, therefore,the dry etch time to complete the gas injection orifice fabrication isexpected to be less than a minute. Once the etch is complete, thephoto-resist 532 is stripped. The process ends in step 550.

Fabrication in silicon has some additional advantages, since it can beuseful in oxide etch processes as a (fluorine) scavenger; however, it isconsumed in time leading to orifice erosion. If so, the performance ofthe gas injection orifices can be observed by monitoring the injectiontotal pressure using pressure sensor 46 (FIG. 4). A reduction in theinjection total pressure can imply erosion of the gas injection orifices(i.e., opening of the gas injection orifices or increase in the minimumcross-sectional area A or reduction in length L). This information canbe used to determine the replacement lifetime of a consumable gasinjection plate 20.

Referring again to FIG. 4, process gas originates in gas supply 48, iscoupled to a mass flow controller 44 to monitor and regulate the flow ofprocess gas, is coupled to the processing region 12 through gasinjection plate 20, and is exhausted via vacuum pump 40. The monitoringand control of the gas injection system is facilitated by controller 42,wherein controller 42 is coupled to gas supply 48, mass flow controller44, pressure sensor 46, chamber pressure sensor 49, substrate holdertranslation device 36 and vacuum pump 40. As a function of time,controller 42 monitors the injection total pressure via pressure sensor46 and an exemplary time trace of pressure is shown in FIG. 12.

When an orifice, such as those depicted in FIGS. 5A–C, is eroded byplasma present on one side of the gas injection orifice, the gasinjection orifice length L decreases in time followed by an increase inthe gas injection orifice throat area once plasma has eroded through theentire length of the gas injection orifice length L. An example ofplasma erosion of a gas injection orifice is shown in FIG. 13. In FIG.13, a (cleaved) cross-section of a gas injection orifice, similar to theone depicted in FIG. 3, is shown where the left end of the orifice hasbeen eroded. A decrease in the orifice L corresponds to a decrease inthe orifice aspect ratio L/d, which, in turn, leads to an increase ofthe discharge coefficient. An increase in the discharge coefficientappears as an increase in the effective throat area and translates intoa decrease in injection total pressure as shown in FIG. 12 (region 600).Moreover, an increase in the throat area is also observed as a decreasein the injection total pressure as shown in FIG. 12 (region 610).However, due to differing rates in which the length L and throatdiameter d vary, the former and latter erosion regimes can bedistinguished by a change in the slope of the pressure trace of FIG. 12.

When the injection total pressure, as shown in FIG. 12, falls below athreshold value, controller 42 can provide an alert to schedule areplacement of the (consumable) gas injection system components.Controller 42 can also counter the degradation of the gas injectionsystem by altering process gas flow properties to compensate for thevariation in the gas injection orifice discharge coefficient and,thereby, extend the lifetime of the consumable.

Using equation (1), the measured injection total pressure can be relatedto the “theoretical” (or isentropic) mass flow rate. By furtherrecording the (real) mass flow rate at the mass flow rate controller 44,a ratio of the real mass flow rate to the isentropic mass flow rateprovides an average discharge coefficient for the gas injection system.When the gas injection orifice is eroded (FIG. 13), the orifice aspectratio L/d decreases, and subsequently, when the injection total pressuredecreases (FIG. 12), the orifice Knudsen number Kn increases. Due to thedecreasing aspect ratio L/d and increasing Knudsen number Kn, thedischarge coefficient changes since, as described with reference to FIG.6, the discharge coefficient is a function of the orifice aspect ratioL/d and the Knudsen number Kn.

Such a variation in the discharge coefficient can be observed as amovement across characteristics (700 and 710) shown in FIG. 14. In FIG.14, a gas injection system is designed to operate at a first point 720on a first characteristic 700. As the discharge coefficient varies andthe process gas mass flow rate is maintained constant (via mass flowcontroller 44), the operating point shifts from first point 720 on thefirst characteristic 700 to second point 730 on second characteristic710. Depending on the dependence of the discharge coefficient on theorifice aspect ratio L/d and the orifice Knudsen number Kn, the secondpoint 730 can have a discharge coefficient greater than (as illustratedin FIG. 14) or less than the discharge coefficient of the first point720. In the case of FIG. 14, by decreasing the mass flow rate to furtherdecrease the injection total pressure, controller 42 moves the operatingpoint from second point 730 on second characteristic 710 to third point740 on second characteristic 710, and return to the design dischargecoefficient of value indicated by the (short) dashed line 750. Byfollowing a control sequence such as discussed, the gas injection systemdischarge coefficient can be held constant and consequently the materialprocessing system 1 can extend use of gas injection consumables prior toreplacement (as long as the process mass flow rate is not substantiallyvaried beyond control limits set for the process recipe).

FIG. 15 illustrates a simplified block diagram of a manufacturing systemin accordance with a preferred embodiment of the invention.Manufacturing system 1500 comprises material processing system 1510,transfer system 1520, and process controller 1530. Transfer system 1520is coupled to material processing system 1510. Process controller 1530is coupled to materials processing system 1510, and to transfer system1520.

Material processing system 1510 comprises at least one processingchamber (not shown) wherein a processing region (not shown) is provided.At least one processing chamber comprises a gas injection manifold towhich a gas injection plate can be removeably attached. Processing gasenters processing chamber through gas injection manifold and gasinjection plate. Additionally, processing chamber provides substrateholder upon which a substrate rests, wherein an upper surface ofsubstrate is exposed to processing region. Furthermore, the substrateholder can be vertically translated by translation device such that thespacing between the exposed surface of substrate and gas injection platecan be varied.

Material processing system 1510 comprises at least one opening (notshown) for loading/unloading semiconductor wafers and at least oneopening (not shown) for loading/unloading gas injection plates. In apreferred embodiment, load lock chambers are arranged outside theopenings. Transfer mechanisms (not shown) for loading/unloading thesemiconductor wafers, and transfer mechanisms (not shown) forloading/unloading the gas injection plates are arranged in therespective load lock chambers. Such transfer mechanisms may include, butare not limited to, at least one robotic arm.

In operation, process controller 1530 determines a process type. Forexample, process controller 1530 determines that an etching process isrequired and the etching process can be performed using materialprocessing system 1510. Process controller 1530 selects a gas injectionplate based on the process type. In a preferred embodiment, at least onegas injection plate is stored in transfer system 1520, and processcontroller sends commands to transfer system 1520 to ensure transfersystem knows where to find the selected gas injection plate.

The selected gas injection plate is transferred into the materialprocessing system using a transfer system (e.g., robotic arm) coupled tothe material processing system, and the gas injection plate is coupledto a gas injection manifold. Further details regarding the coupling ofthe gas injection plate to the gas injection manifold are presented inpending U.S. application 60/219,737 filed on Jul. 20, 2000, which isincorporated herein by reference in its entirety. Process controller1530 determines a wafer to be processed based on the process type. Theselected wafer is transferred into the material processing system usingthe transfer system; the selected wafer is processed; and the processedwafer is transferred out of the material processing system using thetransfer system.

Process controller 1530 determines if an additional wafer requiresprocessing using the process type, and the additional wafer istransferred into the material processing system using the transfersystem when the additional wafer requires processing.

Also, process controller 1530 determines if an additional wafer requiresprocessing using a different process type that requires a different gasinjection plate. The gas injection plate is transferred out of thematerial processing system using the transfer system if the additionalwafer requires processing using the different process type. A differentgas injection plate is selected based on the different process type, andthe different gas injection plate is transferred into the materialprocessing system using the transfer system. The additional wafer istransferred into the material processing system using the transfersystem; the additional wafer is processed using the different processtype; and the processed wafer is transferred out of the materialprocessing system using the transfer system.

In addition, process controller 1530 can control the fabrication of theselected gas injection plate based on the process type. In this regard,process controller 1530 can select a substrate for the plate (alsocalled a “plate substrate”) based on the process type. Materialprocessing system 1510 can be used to etch a plurality of first features522 into a first surface of the plate substrate 512 using a firstpattern based on the process type; and to etch a plurality of secondfeatures 522 through the plate substrate, wherein, a gas injectionorifice comprises a first feature having a depth of at least one half ofthe plate substrate thickness and a second feature comprising a throughhole from the second surface to the first feature. For example, materialprocessing system can comprise a plurality of processing chambers forprocessing wafers and gas injection plates.

The process controller can determine if the operating point of a gasinjection plate is below a threshold; and can send a message to thematerial processing system and/or an operator signaling that gasinjection plate needs to be changed. Alternately, the materialprocessing system can determine if the operating point of a gasinjection plate is below a threshold; and can send a message to theprocess controller and/or an operator signaling that gas injection plateneeds to be changed.

During wafer processing, the process controller can determine if theoperating point of a gas injection plate is below a threshold; and cansend a message to the material processing system to move the operatingpoint above the threshold. Alternately, the material processing systemcan determine if the operating point of a gas injection plate is below athreshold; and can modify at least one process parameter to move theoperating point above the threshold.

In addition, the process controller can determine if the operating pointof a gas injection plate is below a threshold; and can send a message tothe material processing system and the transfer system to change the gasinjection plate. Desirably, the material processing system monitors thewafer and/or plasma conditions during processing to determine if theoperating point of the gas injection plate is below a threshold.Alternately, the wafer and/or the gas injection plate can be examined bythe transfer system to determine if the operating point of the gasinjection plate is below a threshold.

It should be noted that the exemplary embodiments depicted and describedherein set forth the preferred embodiments of the present invention, andare not meant to limit the scope of the claims hereto in any way.Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

1. A method of operating a manufacturing system, wherein themanufacturing system comprises material processing system, transfersystem, and process controller, the method comprising: determining aprocess type; selecting a gas injection plate based on the process type;transferring the gas injection plate into the material processing systemusing the transfer system coupled to the material processing system;coupling the gas injection plate to a gas supply system using theprocess controller; and processing a substrate based on the processtype.
 2. The method of operating a manufacturing system as claimed inclaim 1, further comprising: determining if an additional substraterequires processing using a different gas injection plate; transferringthe gas injection plate out of the material processing system using thetransfer system if the additional substrate requires processing usingthe different gas injection plate; and transferring the different gasinjection plate into the material processing system using the transfersystem.
 3. The method of operating a manufacturing system as claimed inclaim 1, wherein selecting a gas injection plate based on the processtype further comprises: selecting a plate substrate for the gasinjection plate based on the process type; etching a plurality of firstfeatures into a first surface of the plate substrate using a firstpattern based on the process type; and etching a plurality of secondfeatures through the plate substrate, wherein, a gas injection orificecomprises a first feature having a depth of at least one half of theplate substrate thickness and a second feature comprising a through holefrom the second surface to the first feature.
 4. The method of operatinga manufacturing system as claimed in claim 1, wherein processing asubstrate type further comprises: determining a substrate to beprocessed based on the process type; transferring the substrate into thematerial processing system using the transfer system; processing thesubstrate; and transferring the substrate out of the material processingsystem using the transfer system.
 5. The method of operating amanufacturing system as claimed in claim 1, wherein processing asubstrate type further comprises: determining if an operating point ofthe gas injection plate is below a threshold; and signaling that gasinjection plate needs to be changed if the operating point is below thethreshold.
 6. The method of operating a manufacturing system as claimedin claim 1, wherein processing a substrate type further comprises:determining if an operating point of the gas injection plate is below athreshold; and modifying at least one process parameter to move theoperating point above the threshold.
 7. The method of operating amanufacturing system as claimed in claim 1, wherein processing asubstrate type further comprises: determining if an operating point ofthe gas injection plate is below a threshold; and changing the gasinjection plate if the operating point is below the threshold.
 8. Themethod of operating a manufacturing system as claimed in claim 7,wherein determining if the operating point of the gas injection plate isbelow a threshold further comprises monitoring the substrate todetermine if the operating point of the gas injection plate is below athreshold.
 9. The method of operating a manufacturing system as claimedin claim 7, wherein determining if the operating point of the gasinjection plate is below a threshold further comprises monitoring aplasma to determine if the operating point of the gas injection plate isbelow a threshold.
 10. The method of operating a manufacturing system asclaimed in claim 1, further comprising: determining if an additionalsubstrate requires processing using the process type; and transferringthe additional substrate into the material processing system using thetransfer system when the additional wafer requires processing.
 11. Themethod as claimed in claim 1, wherein the substrate comprises asemiconductor wafer.
 12. A manufacturing system comprising: materialprocessing system having a gas supply system; transfer system coupled tothe material processing system; and process controller coupled to thematerials processing system and to the transfer system, wherein theprocess controller determines a process type, selects a gas injectionplate based on the process type, transfers the gas injection plate intothe material processing system using the transfer system, couples thegas injection plate to the gas supply system; and processes a substratebased on the process type.
 13. The manufacturing system as claimed inclaim 11, further comprising means for coupling the gas injection plateto a gas injection manifold.
 14. The manufacturing system as claimed inclaim 12, wherein the transfer system comprises at least one roboticarm.
 15. The manufacturing system as claimed in claim 12, wherein thetransfer system further uncouples the gas injection plate afterprocessing the substrate when a next process type is different than acurrent process type.
 16. The manufacturing system as claimed in claim12, wherein the substrate comprises a wafer.
 17. The manufacturingsystem as claimed in claim 12, wherein the substrate comprises a liquidcrystal display panel.